1. The Contractor shall test environmental chemicals in laboratory animals (in particular, mice or rats, or rabbits), and develop data on the general and reproductive toxicity of such chemicals. 2. There are two kinds of work involved in this contract: 1) evaluating tissues and vaginal cytology slides sent from other toxicology labs (spermatid count and vaginal cytology evaluation, SCVCE), 2) performing in vivo toxicity studies in-house. 3. The Contractor purchase healthy animals from a source approved by the Project Officer, and maintain them in environmentally-controlled facilities with a controlled light cycle and controlled temperature and humidity. 4. The Contractor shall be required to prepare protocols and standard operating procedures (SOPs) for studies as they are needed. 5. There are two parts of the SCVCE work: (1) tissue/slide evaluation and reporting, and (2) technical assistance to other NTP laboratories.